Phagu Purnima is another name for Holi where Phagu means the sacred red powder and Purnima or Pune is the full moon day, on which the festival ends.
At some places like Bihar, Holi is also known as Phagwa as it is celebrated in the later part of the month of Phalgun and the early part of Chaitra in the Hindu calendar. This corresponds to the English months of March-April.
The concept of New Year (Samvatsar) varies in the different provinces of our country. In some provinces, the month commences from the 'Krishna-Paksha' on the other hand in some provinces it commences from 'Shukla-Paksha'. For the former, the year ends on 'Purnima' of the month of Phalgun. The new years begins next day - Chaitra, 1st day of the Krishna Paksha. For them on this day the last year has died. For this reason in some provinces like Bihar and UP. Holika dahan is also called 'Samvatsar Dahan'. On this day all the bitterness and evil memories of the last year are burnt in the fire and the New Year is begun with a celebration.